Hydraulic remote control systems



July 18, 1961 H. .1. NICHOLS 2,992,632

HYDRAULIC REMOTE CONTROL SYSTEMS Original Filed Feb. 21. 1949 INVENTOR. HARRY J. NICH LS ATTORNEY United States Patent 2,992,632 HYDRAULIC REMOTE CONTROL SYSTEMS Harry J. Nichols, 1212 Rue Ave., Point Pleasant, NJ. Filed Nov. 3, 1954, Ser. No. 466,571 6 Claims. (Cl. 121-41) This invention relates to improvements in hydraulic remote control systems and has particular reference to an improved hydraulic remote pitch control system for controllable pitch propellers, the present application being a continuation of my prior application Serial No. 77,635, filed February 21, 1949, now abandoned.

A main object resides in the provision of an improved remote control system characterized by case and flexibility of operation, reliability, accuracy, utmost simplicity, a minimum of component parts, and economy in first cost and operation.

A further object resides in the provision of semiautomatic means for coordinating the movements of the hydraulic servo element which actuates the driven mechanism with the movements of the master control member, whereby the movements of the servo element duplicate exactly those of the master control member.

A still further object resides in the provision of a pitch control system for controllable pitch propellers in which the rmt position of the master pitch control member controls and automatically indicates the pitch of the propeller blades.

Yet another oject resides in the provision of hydraulic means which automatically locks the servo element in any position to which it may be set.

Other objects and advantages will be more particularly pointed out hereinafter or will become apparent as the description proceeds.

In the accompanying drawing, in which like reference numerals and symbols are utilized to designate similar parts throughout, there is illustrated by way of example a suitable mechanical and hydraulic arrangement for the purpose of disclosing the invention. It is to be understood, however, that the drawing is for the purpose of illustration only and is not to be taken as limiting or restricting the invention since it will be apparent to those skilled in the art that various changes in the illustrated arrangement may be resorted to without in any way exceeding the scope of the invention.

The accompanying drawing is a schematic diagram of one embodiment of the invention which illustrates typical component apparatus, hydraulic circuits and the principle of operation of thesystem of the invention as applied, by way of example, to the remote control of the pitch of acontrollable pitch propeller. This example was chosen because, a propeller being carried by a rotating shaft and being totally inaccessible when in use, the practical requirements for this application are exceptionally complex and difficult to fulfill. It follows that the system of the invention will also meet the requirements of numerous other applications of equal or less exacting types.

Referring to the drawing, the controllable pitch propel ler, which is shown schematically, includes a hollow hub, generally indicated at 1, carried by a tubular rotary propeller shaft 2 and in which are rotatably mounted a plurality of blades 3; and pitch changing mechanism mounted therein including a hydraulic servo piston, indicated generally by SP, and crank pins 4, carried by the blades. A pitch changing mechanism suitable for operation by the present invention is particularly illustrated and described in my co-pending application for US. Letters Patent Serial No. 62,017, filed November 26, 1948, now Patent No. 2,786,539, to which reference is made for further details. For present purposes it should be noted that hydraulic servo piston SP, upon axial translation in the bore of the hub, which constitutes a.

2 cylinder, imparts an equal turning moment to each of the blades by means of the crank pins 4. The propeller hub and servo piston thus constitute a double-acting hydraulic servo-motor of fixed cylinder and controlled servo piston type, referred to generally hereinafter as the servo motor SM.

Servo motor SM is also provided with calibrating valve means, here shown for purposes of illustration as opposed spring-loaded ball-check valves V1, V2; although springloaded pin-check valves and other suitable types may be employed instead; which valves are connected by a longitudinal passage 5 servo piston SP as shown. Each valve is assembled in the end of the piston so that the movable member of the valve, say the ball, projects slightly beyond the face of servo piston SP, so as to be actuated when the piston is moved to either of its extreme positions. Thus, as servo piston SP approaches one or the other end of its stroke, the closed valve at that end is opened, thereby permitting pressure fluid to by-pass from the pressure to the exhaust end of the piston, thus limiting the working stroke of the piston. When fluid under pressure is first introduced into the hydraulic system, the calibrating valve means by-passes any trapped air around the piston, permitting such air to be eliminated from the hydraulic system. This same by-passing action also calibrates the stroke of the servo piston with respect to that of the duplicator cylinder DC by regulating the quantity of hydraulic link fluid, as described hereinafter. The calibrating valve means thus serve the combined functions of a pitch-limit device, auxiliary means for bleeding air from the hydraulic system, and an automatic calibrating device, but for brevity such are herein referred to as calibrating valves or calibrating valve means.

Hydraulic fluid under pressure may be supplied to the servo-motor SM through coaxial conduit 6 and through the concentric passage between that conduit and propeller shaft 2. Fluid may be supplied from external hydraulic line 7 into conduit 6, and from external line 8 into the said passage by suitable rotary sealing means, indicated generally at RS, as for example that described in detail inthe aforesaid co-pending application.

Hydraulic duplicator A traveling double-acting duplicator cylinder DC, having a fixed piston FP, with a single end-rod ER, is hydraulically connected in series between the distribution ports of servo-valve SV and servo-motor SM for purposes presently to be explained. The fluid capacity of duplicator cylinder DC should be substantially equal to the volume of fluid displaced by the working stroke of servo-piston SP.

In order to gain compactness and to simplify substantially the hydraulic lines and mechanical connections, duplicator cylinder DC has an integral servo-valve SV, as indicated. The end rod ER may be provided with a olevis pivotally secured to a stationary support member 12, whereby piston FF is held against translation. Because of its special function in the system of the invention, the unitary combination of duplicator cylinder DC and servo-valve SV carried thereby is termed herein a hydraulic duplicator.

Servo-valve SV, which is preferably of 3-position, 4- connection, open-center type, is preferably provided with a spring-centered valve plunger VP, or equivalent. A freely movable master control member CM, shown as a lever pivoted to a stationary support member 13, may be operatively connected to valve plunger VP in any de sired way, provided their movements are coordinated so that they move together. A pressure actuated locking valve LV, sometimes known as a ratchet-valve, comprising a floating actuating piston AP and opposed spring-- Patented July 18, 1961 loaded check valves V3, V4, may be hydraulically connected to the servo-valve SV, and may be made integral therewith, as indicated, to simplify the hydraulic connections. Servo-valve SV is provided with an inletport connected to pressure working line and outlet port connected to exhaust line 11, and two distribution ports which may be directly connected to lock valve LV as indicated; or to one chamber of DC and one chamber of SM in case lock valve LV is omitted. Lock valve LV is provided with ports connected by passages to the distribution ports of servo-valve SV, a port connected directly to the blind end of duplicate cylinder DC, and a port connected to working line 8. The rod end of duplicator cylinder DC is connected to series working line 7, which terminates in the blind chamber of servo-motor SM. The hydraulic fluid enclosed in this working line and the connected chambers constitutes a hydraulic link. Compensating devices, of known type and indicated generally at C0, may be connected to lines 7 and 8 to compensate for the thermal expansion of the working fluid in the locked portion of the hydraulic circuit, should this be desirable in special cases. There are also known types of valves in which the valve plunger when in neutral position shuts the distributing ports, thereby locking the working fluid, as performed by lock valve LV. Hence it is to be understood that the term servo-valve includes the locking valve function.

Controls The master control member CM, which may be located at a station remote from duplicator cylinder DC and connected to valve plunger VP by any suitable linking means which makes them move together, may be operatively associated with an indicator pointer I and a calibrated position scale S, or equivalents, for purposes of visually indicating the pitch, as explained hereinaiter. The servo-valve SV can be actuated by control forces of a weak order, and the control member CM being normally free, the control system of the invention is welladapted for alternative operation from one or more remote stations, which stations can be linked together serially or in parallel. For operation by remote control, any remote master control member could of course be provided with position indicating means, similar to that illustrated; or the position indicating means can be separate and operatively connected to the servo-valve SV or master control member CM. Thus the system of the invention prov-ides an exceptional degree of flexibility in the feasible control arrangements, while giving an ease of operation commonly called touch-control.

Operation The operation of the pitch control system Whose components were described above is as follows: All the working pants are assumed to be in mid position and the blades in neutral pitch, as indicated by their position and the pitch indicator being at neutral position N on the scale S. When the system is in non-operating condition, the servo-valve SV is open and fluid passes freely from pressure line 10 via the servo-valve ports to exhaust line 11. The pump P therefore normally runs unloaded and absorbs the minimum of driving power. This is an important practical feature of the system which saves power When idling, which it does nearly all the time, and greatly prolongs the life of the pump and pump driving means. This feature also enables substantial power savings when the hydraulic system must deliver a substantial amount of power, as for example in the operation of controllable pitch propellers on ships.

When the pitch control member CM is moved clockwise towards the Ahead position, indicated at A on the scale, valve plunger VP will be shifted to the right, thereby applying pressure fluid to the left distribution port; whereupon fluid will flow in thehydraulic circuits as indicated by the small arrows. Pressure fluid pushes actuating'piston A? of lock valve LV to the right, thus open- 4 ing check valve V4 and admitting pressure fluid to the head end of duplicator cylinder DC. Since the fixed piston FF is held stationary by its support, the duplicator cylinder is forced to move to the right, thereby displacing fluid under pressure from the rod end of the cylinder via line 7 and conduit 6 into the outboard end of servo motor SM. This fluid pushes servo-piston SP to the right, thereby turning the blades so as to cause an increase of pitch.

I Due however to the follow-up movement imparted to the servo-valve SV by duplicator cylinder DC, the servov'alve exhaust ports tend to re-open as the pitch is changed, and unless the movement of the control member CM is continued, the pitch changing cycle will be termin-ated by such follow-up movement, due to return of the servo-valve to open-center condition. When this occurs, the pressure on actuating piston AP is released and both check valves V3 and V4 promptly close, thus locking the working fluid in the connections to duplicator cylinder DC and servo-motor SM. Thus, the servo-piston SP is locked hydraulically in any set position.

It should also be observed that valve plunger VP when initially displaced produces some compression of one or the other centering spring. Upon release of control member CM, any lost motion which mayhave occurred will be restored by the centering springs, thus producing an accurate pitch indication. Provided, of course, control member CM is permitted to move freely upon release, as it should in practice. However, if control member CM cannot move freely, the only consequence would be a slight error in pitch indication, and the pump P might possibly operated under partial load, rather than no load, due to olf-centering of valve plunger VP.

To decrease or reverse the pitch, the control member CM is simply moved counter-clockwise towards the Reverse position, indicated by R on the scale, whereupon valve plunger VP will be displaced to the left and an operational cycle of the same order but opposite in direction will be performed.

Synchronization Detailed analysis will show that the movement of servopiston SP will be exactly proportional to the movement of duplicator cylinder DC, provided there is no leakage affecting the hydraulic link connecting these components. This follows from the fact that the linking fluid is displaced directly from duplicator cylinder DC into servo cylinder SM, and vice versa. Further, duplicator cylinder DC carries with it servo valve SV, and the movement of the latter in efiect measures the quantity of linking fluid transferred between the cylinders. At the end of an operating movement, lock valve LV positively locks the working fluid. in the normally closed portion of the system so as to prevent any change of the set pitch. Leakage in the servo-valve will not affect the pitch setting. Hence, if adequate hydraulic packings are provided and the system is properly calibrated, synchronism will be maintained indefinitely between the movements of the master control member and the servo element. These features contribute importantly to the characteristic accuracy and reliability of the system.

However, should any leakage occur in any portion of the hydraulic circuits which might cause a loss of calibration or synchronism, the system can be immediately recalibrated as follows: the control member CM is moved to one extreme position, then to the other, to reverse the stroke of servo-piston SP completely. Should servo piston SP reach the end of its stroke before duplicator cylinder DC reaches the end of its stroke, fluid will be by-passed around servo-piston SP by action of the calibrating valve means; and upon reversing the stroke, the system will be resynchronized. Vice versa, the system will be calibrated at the other end of the servo-pistonstroke.

Such check of the calibration would of course i be part of the regular routine check of the control sys- I system is in operation, and would be performed auto matically whenever a complete reversal cycle is performed. i r I It seems evident without further discussion that the semi-automatic calibrating feature provided by the present invention is of vital practica'limportarice; and overcomes a major defect of some systems of the prior art, in which any loss of calibration involved extensive and inconvenient .remedial measures.

It should be noted that the remote control system of the invention=constitutes a complete'servo-systemof position-control type; in which master control member CM constitutes the input member, servo-piston SP the position controlledor servo element; the driven mechanism the load; duplicator cylinder DC and servo-valve SV the differential error detecting device; the pump P and servo-valve SV the power source and amplifier; and the lock valve LV or equivalent the stabilizing device.

While a particular mechanical and hydraulic arrangement has been illustrated in the accompanying drawings and hereinabove described forthe purpose of disclosing the invention, it is to be understood that the invention is not limited to the particular construction and arrangement so illustrated and described, but that various changes in the size, shape and arrangements of the various parts may be resorted to within the scopeoff the subjoined claims.

Having now described the invention so that others skilled in the art may clearly understand the same, what it is desired to'secure by Letters Patent is as follows:

I claim:

1. In a hydraulic remote control system of servo type, the combination of: a power source of hydraulic pressure fluid; a hydraulic servo-motor having a working servo element displaceable by pressure fluid; a traveling unitary hydraulic duplicator mechanically independent of said servo-motor and comprising a double-acting hydraulic cylinder having a displacement capacity substantially equal to that of said servo-motor and an integral servo-valve, said cylinder having a stationary piston and being reciprocable relative thereto by pressure fluid, and said servo valve having a translatable valve plunger and valve ports arranged to control the supply of pres sure fluid from said source to either said servo-motor or said cylinder according to the relative movements of said plunger and said ports; a hydraulic link serially connecting said servo-motor and said cylinder whereby they are jointly controlled by said servo-valve; a freely movable master control member operatively connected to said valve plunger so as to translate same; and means including automatic calibrating valve means actuated by said servo element for synchronizing the movements of said servo element with those of said master control member; whereby the rest position of said member controls and indicates the displacement of said servo element.

2. In a hydraulic remote control system of servo type including a power source of hydraulic pressure fluid, the combination of: a double-acting servo-motor having a servo element displaceable by pressure fluid; a traveling unitary hydraulic duplicator mechanically independent of said servo motor and comprising a double-acting hydraulic cylinder having a displacement capacity substantially equal to that of said servo-motor and an integral servo-valve, said cylinder having a stationary piston and being reciprocable relative thereto by pressure fluid, and said servo-valve having a movable valve plunger and valve ports arranged to control the supply of pressure fluid from said source to either said servo motor or said cylinder according to the relative movements of said plunger and said ports; a hydraulic link serially connecting said servo-motor and said cylinder whereby they are jointly controlled by said servo valve; a freely movable master control member operatively connected to said valve plunger so that they move together; and means including automatic valve means actuated by said servo elementfor synchronizing the movements of said servo element with those of said master control member; whereby the posi and indicates the displacetion of said member controls ment of said element.

3. In a hydraulic remote control system of servo type including a power source of hydraulic pressure fluid, the

combination of: a double-acting servo-motor having af servo element settable by pressure fluid; a traveling unitary hydraulic duplicator mechanically independent of said servo-motor and comprising a double-acting hydrau lic cylinder having a displacement capacity substantially equal to that of said servo-motorand an integral servo valve, said cylinder having a stationary piston and being reciprocable relative thereto by pressure fluid, and said servo-valve having a movable valve plunger and valve ports arranged to control the supply of pressure fluid to either said servo-motor or said cylinder according to the relative movements of said plunger and said ports and having working fluid locking means; a hydrauliclink serially connecting said servo-motor and said cylinder whereby they are jointly controlled by said; servo-valve; a freely movable master control member operati velylconnected to said valve plunger so that they movelrtogether; and means including calibrating valve means actuated by said servo element for synchronizing 1 the movements of said servo. element with. those of said master control member; whereby the rest position of said member controls and indicates the setting of said element and said element is hydraulically locked in such setting.

4. A hydraulic remote control system comprising, in combination; a hydraulic servo-motor having two chambers for pressure fluid and a servo member reciprocable by fluid pressure; a hydraulic duplicator remote from and mechanically independent of said servo-motor and comprising an integral hydraulic cylinder and servo-valve, said cylinder having two chambers for pressure fluid substantially equal in capacity to the chambers of said servomotor and a stationary piston, whereby said duplicator is reciprocable with respect to said piston by fluid pressure, and said servo-valve having two fluid distribution valve ports and a movable valve plunger for controlling the passage of fluid through said ports; a power source of hydraplic fluid; a hydraulic circuit interconnecting said source and said servo-valve for transferring fluid therebetween, a hydraulic connection between one of said distribution ports and one chamber of said servo-motor, a hydraulic connection in said duplicator between the other of said distribution ports and one chamber of said hydraulic cylinder, and a hydraulic link serially connecting the others of said chambers, whereby said servo-motor and said hydraulic cylinder are reversibly controlled by said valve plunger in accordance with its position relative to said ports; a freely movable remote control member operatively connected to said valve plunger; and automatic calibrating valve means actuated by said servo member for regulating the quantity of fluid in said hydraulic link; whereby in operation said servo member and said duplicator perform duplicate movements and follow precisely the movements of said control member.

5. In a hydraulic remote control system including a power source of pressure fluid, the combination of a hydraulic servo-motor having two chambers for fluid and a working servo member reciprocable by fluid pressure therein; a hydraulic duplicator mechanically independent of said servo-motor and comprising a stationary piston, a movable cylinder member having two chambers for fluid and reciprocable with respect to said piston by fluid pressure, and a fluid control servo-valve carried bodily by said cylinder, said valve having two fluid distribution ports and a movable plunger for controlling the passage of fluid through said ports, and said chambers having a displacement capacity substantially equal to those of said servo-motor; a hydraulic circuit between said source and said valve for transferring fluid therebetween; a hydraulic connectionbetweem one of said ports and one chamber of said servo-motor; a hydraulic connection in said duplicatorzbetweeni the other'of said; ports and one chamber ofsaid cylinder; and a closed, hydraulic connection between the others of said chambers; the fluid in said closed connection and chambers constituting a hydraulic link serially conneotingisaid motor and said duplicator, where. by saidzplunger actuates them jointly in accordance with its. position relative to said port-s; afreely movable remote? control membervoperatively connected to said plunger;

and semi-automatic means, including calibrating valve means openableby said= servo member at either end: of its stroke, for coordinating hydraulically the movements of said servo member andsaid movable cylinder; whereby the cylinder of the duplicator duplicates the movements of said servo member and the latter follows the movements of the remote control member.

6. In a hydraulic remotev control system including a power source of hydraulic fluid under pressure, the combination comprising: a' double-acting hydraulic servo motor having a servo-piston reciprocable by fluid under pressure; a freely movable control member remote from said motor; means for. controlling. quantitively the'supply ofv fluid under pressure to said motor includingv a fluid'reciprocable duplicator :cylinder having a stationary piston andofa displacement capacity substantially equal to'that of said' motor and connected-hydraulically in series there of said'member; and automatic calibrating valve'meansin and actuated by said servo-piston at either end of its stroke for regulating the quantity of fluid inter-connecting saidmotor andsaid cylinder; whereby said member con trols and indicates the position of said servo-piston.

References Cited in'the fileofi this patent UNITED STATES PATENTS 1,955,154 Temple Apr. 17, 1934 1,965,867 Vickers July 10, 1934 2,261,444 Neubert NOV. 4,1941 2,345,531 Ganahl Mar. 28, 1944 2,388,010 Pohl Oct. 1945 2,395,671 Kleinhans eta1. 'Feb. 26, 1946 2,524,055 Hubert Oct. 3, ,1950 2,573,943 Zislal Nov. 6,1951 2,637,259 Acton May 5, 1953 2,786,539 Nichols, Mar. 26, 1957 V FOREIGN PATENTS France June 10, 1929- 

